Caption: E. coli O157 bacteria. Coloured transmission electron micrograph (TEM) of a section through Escherichia coli O157 bacteria, a cause of food- borne illness. E. coli are Gram-negative intestinal bacteria (enterobacteria). Infection with the O157 strain can result in bloody diarrhoea and kidney failure, particularly in the elderly and very young. It is found in the intestines of some cattle, and can spread to contaminate beef and milk. Its transmission can be prevented by thoroughly cooking meat and through the pasteurisation of milk. Magnification: x5800 at 6x7cm size.